DenyHosts: Denial of Service
DenyHosts does not correctly parse log entries, potentially causing a
remote Denial of Service.
denyhosts2007-10-132007-10-13181213remote2.6-r12.6-r1

DenyHosts is designed to monitor SSH servers for repeated failed login
attempts.

Daniel B. Cid discovered that DenyHosts used an incomplete regular
expression to parse failed login attempts, a different issue than GLSA
200701-01.

A remote unauthenticated attacker can add arbitrary hosts into the
blacklist, including the "all" keyword, by submitting specially crafted
version identification strings to the SSH server banner. An attacker
may use this to prevent legitimate users from accessing a host
remotely.